invention relates to a roof valley flashing and more particularly to a flashing formed of a unitary sheet of durable plastic material.
In a roof construction where two roof planes join at a valley, it has long been recognized that there are special problems in sealing to avoid leaks. The roof top environment is harsh and flashing structures placed in such valleys are expected to endure for many years despite exposure to intense sun, wind, rain, snow and ice, occasional walking on by roofers or other tradesmen, and temperature variations of as much as 100 degrees F. Sources of leaks through and around flashing include seams between metal pieces which open up due to temperature expansion causing failure of sealing material such as mastic; rusting of the flashing due to failure of the galvanized layer, in some cases because of electrolytic action around roofing nails; or build-up of ice in the valley causing water to be forced up under adjacent shingles or other roofing material. Certain sealing material simply becomes hard through aging in the environment and no longer retains the flexibility to provide effective seals.
Because of the above problems, the installation of such flashing structures in roof valleys typically requires the services of workmen having a substantial level of skill to avoid costly leaks.
There is, therefore, a need for a flashing structure to be installed in roof valleys which is sufficiently durable to withstand the above described environmental conditions, which is comparatively inexpensive, and which can be installed in a relatively short time by workmen having limited skill and experiences.